Grinding machine



April 7, 1970 R. D. RUTT 3,504,458

GRINDING MACHINE Filed July 19, 19a? 2 Sheets-Sheet 1 INVENTOR. RICHARD D. RUTT April 7, 1970 Filed July 19, 1967 GRINDING MACHINE R. D. RUTT 2 Sheets-Sheet 2 United States Patent 3,504,458 GRINDING MACHINE Richard D. Rutt, Wilson, N.Y., assignor to The Carhorundum Company, Niagara Falls, N.Y. Filed July 19, 1967, Ser. No. 654,422 Int. Cl. 1324b 21/18 US. Cl. 51-435 6 Claims ABSTRACT OF THE DISCLOSURE A grinding machine having a tracking roll pivotable about an axis perpendicular to the longitudinal axis of the roll. An extension arm is provided at the end of the roll and is moveable back and forth between a pair of spaced stops for limiting the oscillating movement of the roll. A double acting hydraulic cylinder is provided for adjusting the oscillation range of the roll by moving the stops in unison when the extension arm tends to dwell against one of the stops.

This invention relates to grinding machines and, more particularly, to means for controlling the tracking of an abrasive belt on a grinding head.

In grinding machines of the type employing abrasive belts, it is generally known to provide a grinding head having a tracking roll and a contact roll about which an endless abrasive belt is trained for movement in an orbital path. Because of fabrication problems and varying stretch characteristics of an abrasive belt, the belt defines an orbital path that is not a true cylinder and tends to move axially off the rolls. Accordingly, means are provided for controlling oscillation of the belt on the rolls to retain the belt thereon. These means may assume various forms but a common expedient is to provide control means responsive to lateral movement of the belt to move the tracking roll about an axis substantially perpendicular to the longitudinal axis of the tracking roll to steer the belt in the direction desired. The end of the tracking roll is provided with an extension which is disposed between a pair of spaced stop nuts for mechanically limiting arcuate movement of the end of the tracking roll. The stop nuts are mounted on a screw which is manually rotated through means of a Worm connection. Due to the change in the geometry of an abrasive belt in use, it will not oscillate uniformly causing the extension to dwell against one of the stop nuts. The operator rotates the screw to laterally move the stop nuts in unison until the belt against oscillates uniformly.

A major problem experienced with these manually operable devices is that the operators attention is constantly required to adjust the stop nuts to maintain uniform belt oscillation. In the event an operator fails to notice, and correct for, a change in oscillation uniformity, the tracking pulley extension arm will dwell against one of the stop nuts for an increasing period of time. The edge of the belt will quickly move in one direction and slowly return until the changing belt geometry requires stop adjustment beyond the manually imposed limitation, at which time the belt continues in one direction even though pressure is being applied to direct the belt in the other direction. This may result in a broken belt which impairs efliciency and represents excessive costs.

The tracking control means of the present invention, as hereinafter described, provides a solution to the above 3,584,458 Patented Apr. 7, 1970 ice problem by providing control means for correcting nonuniformity of belt oscillation by automatically moving the stops laterally when the tracking roll extension tends to dwell against one of the stops.

It is, therefore, an object of the present invention to provide a new and improved grinding machine.

It is another object of the present invention to provide a new and improved grinding machine having novel means for controlling belt tracking.

It is a further object of the present invention to provide a new and improved grinding machine having novel means for automatically maintaining uniformity of belt oscillation on a grinding head.

It is still another object of the present invention to provide a new and improved grinding machine being novel belt tracking control means which is capable of relatively trouble-free operation, requires little maintenance and has a minimum of moving parts.

These and other objects of this invention will become more apparent upon consideration of the following detailed description thereof when taken in conjunction with the following drawings, in which:

FIG. 1 is an isometric view of a grinding machine in which a preferred illustrative embodiment of the invention is incorporated;

FIG. 2 is an enlarged, fragmentary, end elevational view of the belt tracking means for controlling uniformity of belt oscillation constructed in accordance with the principles of this invention;

FIG. 3 is an enlarged, fragmentary view of the belt tracking control means looking in the direction of the arrow 33 of FIG. 2;

FIG. 4 is a diagrammatic view illustrating the fluid circuit for the tracking roll; and

FIG. 5 is a diagrammatic view illustrating the fluid circuit for the tracking control means.

Referring to the drawings, and particularly to FIG. 1, it will be observed that a preferred embodiment of the invention constructed in accordance with the principles of this invention is incorporated in a grinding machine, generally designated 10, having a frame 12 suitably supported on a ground surface. Frame 12 contains a grinding head, generally desginated 16, having a tracking roll 18 and a contact roll (not shown). An endless abrasive belt 22 is trained about both rolls for movement in an orbital path. Although preferably the contact roll is driven by any suitable power means (not shown), tracking roll 18 may be driven instead Within the purview of the present invention. The shaft of the contact roll is journalled at one end in a bearing block 17 having a lug 19 extending therefrom. An elongated arm 20 is pivotally mouted on frame 12 about a horizontal pivot 21 and is provided with a slot 22 for receiving the lug 19 and retaining the contact roll in the proper position relative to the workpiece support.

Frame 12 is provided with beams 24 and 26 extending outwardly from both ends thereof and disposed on both sides of the frame for supporting rollers 28 and 30 journalled for rotation in bearings 32 and 34 mounted adjacent the ends of beams 24 and 26, respectively. An endless conveyor belt 36 is trained about rollers 28 and 30 for the purpose of advancing workpieces beneath abrasive belt 22 in the direction of the arrow shown in FIG. 1. The means for driving the conveyor belt 36 may be of any conventional variety, and since many such arrangements are known in the art, no illustration or further explanation is believed necessary.

The tracking roll 18 is illustrated as being mounted by means of a yoke, generally designated 38, having upstanding journal members 40 and 42 for receiving the opposite ends of the tracking roll shaft 44 and secured to a base 46 which is suitably mounted to the framework of grinding head 16 for pivotable movement about a vertical pivot 48.

A pair of fluid power means, such as pneumatic cylinders 50 and 52 containing pistons having piston rods 54 and 56, respectively, are connected to one end of the base 46 on opposite sides thereof to pivot said base 46 and thereby tracking roll 18 back and forth about the vertical pivot 48.

For controlling horizontal pivotable movement of the tracking roll 18 and thereby lateral oscillation of the abrasive belt 22 along the roll, an air discharge jet 58, having a discharge orifice 60 is suitably mounted on a bracket 62, in turn secured to the grinding head 16. The air jet impinges against a swingable paddle 64 which is connected to an electrical switch 66. A solenoid operated air directional valve 68 acts in response to this switch to direct air to cylinder 50 or 52 as will hereinafter be more fully explained.

Referring now to the diagrammatic showing of the pneumatic circuit in FIG, 4, it will be observed that a pressure line 80 is connected to a suitable source of air (not shown) and is provided with a filter 82 for purifying the air before it enters the system. Pressure line 80 is connected to a control valve 84 having a spool valve, the position of which is controlled by a switch on the control panel 86 for directing or exhausting air from a pressure line 88. Connected to line 88 is a release valve 90 which in turn is connected to the air discharge jet 58 by means of conduit 91. Also connected to line "88 is a release valve 92 which in turn is connected by means of conduit 94 to a directional valve 68 having a spool valve, the position of which is controlled by a solenoid 95 and a spring 97.

Leading from directional valve 68 is a conduit 96 connected to cylinder 50, conduit 96 being provided with a restricted passageway 98 therein to slow the flow of fluid in one direction but may be bypassed in the return direction by a conduit having a check valve 100. Also leading from directional valve 68 is a conduit 102 connected to cylinder 52, conduit 2 being provided with a restricted passageway 104 therein to slow the flow of fluid in one direction but may be bypassed in the return direction by a conduit having a check valve 106.

It will be understood that as the air jet impinges on paddle 64 to swing the same upwardly and activate switch 66, solenoid 95 is actuated to displace the spool valve within directional valve 68 to connect conduit 94 to conduit 102 and apply pressure to the head end of cylinder 52. Piston rod 56 is extended and moves the tracking roll in an arcuate counterclockwise direction as shown in FIG. 1 to move the belt 22 laterally toward the discharge orifice 60. When the discharge orifice 60 is obstructed by the abrasive belt, paddle 64 will fall downwardly by gravity and de-energize solenoid 95 allowing spring 97 to displace the spool valve within directional valve 68 and apply pressure to the head end of cylinder 50 (this is the condition shown in FIG. 4) and exhaust pressure from the head end of cylinder 52 causing the belt to move laterally away from the discharge orifice 60.

It is well-known by those skilled in the art that the ends of the tracking roll move through an arc and the length of this arc, or the number of degrees of motion, must be mechanically limited. The important feature of this invention is the provision of a tracking control means which provides automatic control for adjusting the mechanical limiting means. With reference to FIGS. 2, 3, and 4, such tracking control means, generally designated 110, comprises an elongated bracket 112 suitably secured to the yoke 38 by means of suitable bolts 114. An extension arm 116 extends downwardly from bracket 112 and is provided with a bore 118 adjacent the free end thereof for a reason hereinafter described.

Suitably secured onto the relatively stationary structure of the grinding head is a tracking cylinder assembly, generally designated 126, comprising a double acting cylinder 127, having a piston and a piston rod 128 secured to said piston. Piston rod 128 has a reduced diameter threaded stem portion 130 that extends through a bore 132 of a stop member 134. A washer 136 and a second washer 138 of reduced diameter are disposed about the threaded stem portion 130 against the stop member 134. A stop not 140* is threaded onto the threaded stem portion 130 and spaced from stop member 134 to provide limited axial movement of arm 116. A washer 142 and a second washer 144 of reduced diameter are disposed about the threaded stern portion 130 against stop nut 140.

Suitably secured to and extending from the relatively stationary structure of the grinding head 16 is a threaded stud having a pair of axially spaced stop nuts 152 and 154 for a purpose hereinafter explained.

If, due to the varying stretch characteristics of the abrasive belt whereby the belt does not define a true cylinder and tends to move axially ofi the rolls and the extension arm 116 dwells against one of the stops, i.e., 134 or 140, the force exerted on the piston in the double acting cylinder 127 will effect axial movement of the stops 13-4 and 140 in the direction in which arm 116 is biased to free the same and establish a new range of oscillation for the tracking roll.

Illustrating assembly 126 diagrammatically, it will be seen that the head end of cylinder 127 is connected to the reservoir by means of conduit 162. A restricted passage 164 is provided in conduit 162 to impede the flow of fluid in one direction but may be bypassed in the return direction by a conduit having a check valve 166. A conduit 168 leads from conduit 162 through a restricted passage 170 to the piston rod end of cylinder 127 and may be bypassed in the return direction by a conduit having a check valve 172.

In operation, if extension arm 116 tends to dwell against stop member 134, for example, pressure will be applied on the piston rod side of the piston in cylinder 127 and force the flow of fluid through passage 164, conduit 162, conduit 168, check valve 172 to the piston rod side of cylinder 127. Any excess volume will be received by reservoir 160. Alternatively, if arm 116 tends to dwell against stop 140, fluid will flow from the piston rod side of cylinder 127, through passage 170, conduit 168, conduit 162, check valve 166 into the head end of cylinder 127. Thus, both ends of cylinder 127 are interconnected to effect automatic lateral adjustment of the spaced stop member 134 and stop nut 140 in unison to adjust the oscillation range of the abrasive belt and thereby maintain oscillation uniformity. If desired, nuts 152 and 154 may be adjusted longitudinally of stud 150 to enlarge or restrict the overall oscillation range.

A preferred embodiment of this invention having been described and illustrated, it is to be realized that modifications thereof may be made without departing from the broad spirit and scope of this invention as defined in the appended claims.

I claim:

'1. A grinding machine comprising: a frame; a grinding head mounted on said frame and having a drive roll and a tracking roll; an endless abrasive belt carried by said drive roll and said tracking roll for movement in an orbital path; said tracking roll mounted for pivotable. movement about a pivot axis perpendicular to the longitudinal axis of said roll; means mounted on said frame for oscillating said tracking roll about said pivot axis to effect axial reciprocation of said abrasive belt on said rolls; means carried by said head for limiting the oscillating movement of said tracking roll within a given range between two positions; and means responsive to said tracking roll dwelling at either of said positions for adjusting said limiting means for changing the range of oscillating movement of said tracking roll.

2. A grinding machine as defined in claim 1 wherein said means for adjusting said limiting means comprises a pressure fluid means.

3. A grinding machine as defined in claim 2 wherein said pressure fluid means comprises a double acting hydraulic cylinder having a piston, a piston rod connected to said piston, and said piston rod having a threaded stem portion.

4. A grinding machine as defined in claim 3 wherein 10 said limiting means comprises a pair of spaced stops carried by said threaded stem portion of said piston rod.

5. A grinding machine as defined in claim 4 wherein said tracking roll is provided with extension means moveable between said spaced stops.

6. A grinding machine as defined in claim 5 whereby a prolonged dwell of the extension means against one of said stops effects movement of said stops in unison against the bias of said pressure fluid means.

References Cited UNITED STATES PATENTS 2,597,256 5/1952 Murray 5l-135 2,733,555 2/1956 Dugie et a1 51135 2,813,382 11/1957 Pendergast 51-135 3,325,947 6/1967 Burt 51138 3,363,366 1/1968 Estabrook 51-135 OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 

